1. Technical Field
The present invention relates to a push switch used as an input operating unit of various electronic devices.
2. Description of the Related Art
Recently, various electronic devices are made compact, light-weight, and thin and have multiple functions. There is strong demand for a compact and thin push switch used as an operating unit of the electronic device with excellent feeling at the time of operation.
Such a conventional push switch is described with reference to FIGS. 5 to 7.
FIG. 5 is a cross-sectional view of the conventional push switch, FIG. 6 is an exploded perspective view of the conventional push switch, and FIG. 7 is a cross-sectional view of the conventional push switch in a pressing operation state. In FIGS. 5 to 7, a reference sign 1 represents a case formed of a synthetic resin into a substantially rectangular shape as seen from above having a concave portion with an opening on an upper portion thereof. Central fixed contact 2 having a truncated cone shape with a substantially circular shape as seen from above formed so as to slightly project upward is provided at the center of a bottom surface of the concave portion of case 1. Outer fixed contacts 3 formed to have a rectangular shape as seen from above so as to slightly project upward are provided in two positions point symmetric with respect to central fixed contact 2 in case 1. Terminal 2A connected to central fixed contact 2 and terminal 3A connected to outer fixed contact 3 are derived from case 1 outward.
Case 1 is formed by insert molding of central fixed contact 2, outer fixed contact 3, and terminals 2A and 3A corresponding to them.
A reference sign 5 represents a movable contact having an upward convex dome shape formed of an elastic metal thin plate with surface treatment with excellent conductivity applied to a lower surface thereof. A lower end of an outer edge of movable contact 5 is put on outer fixed contact 3 to be mounted in the concave portion of case 1. A lower surface of a central portion of movable contact 5 is opposed to an upper surface of central fixed contact 2 with a gap therebetween.
A reference sign 7 represents a protecting sheet formed of an insulating film having flexibility and acrylic adhesive 7A, for example, is applied to a lower surface of protecting sheet 7. Protecting sheet 7 is adhered to an upper surface of an outer periphery of case 1 with adhesive 7A on the lower surface thereof so as to cover the concave portion of case 1. A lower surface of a central portion of protecting sheet 7 is adhered to an upper surface of a central portion of movable contact 5.
A reference sign 9 represents a substantially cylindrical pressing projection formed of an insulating resin. Pressing projection 9 is arranged on an upper surface of protecting sheet 7 corresponding to the center of movable contact 5 to be adhered to protecting sheet 7 with an adhesive (not illustrated) formed on a lower surface of pressing projection 9.
The conventional push switch is configured as described above and operation thereof is described as follows.
When pressing projection 9 is pressed downward, pressing force is applied to the central portion of movable contact 5 through protecting sheet 7 below the same. When the pressing force becomes larger than predetermined force, as illustrated in FIG. 7, the central portion having the dome shape of movable contact 5 is elastically inverted so as to be convex downward with click feeling and the lower surface of the central portion of movable contact 5 is brought into contact with central fixed contact 2 below the same. According to this, a switch-on state in which outer fixed contact 3 and central fixed contact 2 are brought into conduction through movable contact 5 and corresponding terminals 2A and 3A are brought into conduction is obtained.
When the pressing force is released, the central portion having the dome shape of movable contact 5 elastically returns to its original upward convex shape together with the click feeling. According to this, it returns to a switch-off state in which the lower surface of the central portion of movable contact 5 separates from central fixed contact 2 and corresponding terminals 2A and 3A are insulated from each other.
Meanwhile, Unexamined Japanese Patent Publication No. 2011-243476 is known, for example, as a conventional art document related to the invention of this application.